The present invention relates to boronated biopolymer crosslinking agents for use in viscosifying treatment fluids and methods relating thereto.
Viscosified treatment fluids are used in many subterranean operations. For example, in fracturing and gravel packing operations, viscosified treatment fluids may be used to suspend and transport particulates to a desired location in a wellbore penetrating the subterranean formation and/or the subterranean formation, so as to form a particulate pack therein (e.g., a proppant pack or a gravel pack). In other instances, viscosified treatment fluids may act to transfer hydraulic pressure in a fracturing operation or to prevent undesired leak-off of fluids into the subterranean formation in a variety of subterranean operations. In many instances, during or after the operation the viscosified treatment fluid is broken (i.e., treated to reduce the viscosity of the treatment fluid) so that the fluid may be more effectively and efficiently removed from the wellbore or formation.
In many instances, viscosified treatment fluids include a base polymer compound that is crosslinked with a crosslinking agent. Common crosslinking agents include metals like boron, aluminum, zirconium, and titanium. However, zirconium and titanium-containing crosslinking agents are used to a lesser degree because of their cost and their crosslinking strength makes the crosslinked fluids difficult to break. Boron-containing crosslinking agents, on the other hand, are more widely available. However, viscosified fluids using boron-containing crosslinking agents are more susceptible to shear thinning wherein the viscosity of the treatment fluid reduces when the fluid is placed under shear. Reduced viscosity can lead to particulate settling in undesired locations, a depressed maximum hydraulic pressure transfer capability, fluids leaking-off into the formation, and the like. To overcome this propensity, boron crosslinking agents typically are added in excess of the stoichiometric amount required to crosslink the treatment fluids, which may increase the environmental footprint and the costs associated with the treatment fluid.